Tocolytics for preterm labor: a systematic review

To examine the effectiveness of any tocolytic compared with a placebo or no tocolytic for preterm labor.

We checked MEDLINE (1966-1998) and the Cochrane Controlled Trials Register for articles, using the search terms "randomized controlled trial" (RCT), "preterm labor," "tocolysis," "betamimetics," "ritodrine," "terbutaline," "hexaprenaline," "isoxuprine," "prostaglandin synthetase inhibitors," "indomethacin," "sulindac," "calcium channel blockers," "nifedipine," "oxytocin receptor blockers," "atosiban," "nitroglceride," and "magnesium sulfate."

We included all RCTs that compared effect of a tocolytic with a placebo or no tocolytic in women in preterm labor, and reported perinatal, neonatal, or maternal outcomes. Studies were excluded if loss to follow-up exceeded 20% of those originally enrolled, or if data were not reported on a per-patient-treated basis. Eighteen of 76 articles retrieved met the inclusion criteria.

Two authors independently reviewed the articles and abstracted the data. Discrepancies were resolved by consensus. Meta-analyses (odds ratio [OR] and 95% confidence interval [CI]) were done for each outcome for all trials and for specific types of tocolytic therapy when possible. Tocolytics decreased the risk of delivery within 7 days (OR 0.60, 95% CI 0.38, 0.95). Betamimetics, indomethacin, atosiban, and ethanol, but not magnesium sulfate, were associated with significant prolongations in pregnancy. Tocolytics were not associated with improved perinatal outcomes. Maternal side effects significantly associated with tocolytic use were palpitations, nausea, tremor, chorioamnionitis, hyperglycemia, hypokalemia, and need to discontinue treatment.

Although tocolytics prolong pregnancy, they have not been shown to improve perinatal or neonatal outcomes and have adverse effects on women in preterm labor.